<html>
<head>
</head>
<body>
<h1 id="title">call js</h1>
<script type="text/javascript">
    function fromFlutter(title){
      document.getElementById("title").innerHTML = title;
      sendBack();
    }
    function sendBack() {
       messageHandler.postMessage("Hello from JS");
    }
</script>
</body>
</html>